1. Field of the Invention
The present invention relates to a cooling apparatus for cooling a heating body by evaporating and condensing refrigerant contained in a tank on which the heating body is attached.
2. Description of the Related Art
Conventionally, a cooling apparatus has a refrigerant tank storing refrigerant and a radiator mounted at the top of the refrigerant tank. The refrigerant having absorbed heat from the heating body and boiled in the refrigerant tank moves from the refrigerant tank to the radiator and is cooled by the radiator, and then condensed into a liquid. After that, the refrigerant returns to the refrigerant tank again. Heat emitted by the heating body is released to outside as latent heat of condensation as the refrigerant condenses at the radiator.
In recent years, due to a demand for portable terminals and the like, there has been a need for cooling apparatuses which can be used in any attitude. However, in the conventional cooling apparatus, it is a problem how to supply the refrigerant to the refrigerant tank. For example, when the cooling apparatus is used upside-down (i.e. with the refrigerant tank at the top and the radiator at the bottom), because the refrigerant is collectted in the radiator and cannot be supplied to the refrigerant tank, the cooling apparatus cannot be used for cooling.
In order to meet such a need, U.S. patent application "COOLING APPARATUS USING BOILING AND CONDENSING REFRIGERANT", Ser. No. 08/978,488, was filed on Nov. 25, 1997. This cooling apparatus is for cooling a CPU such as a semiconductor integrated circuit.
In the cooling apparatus, a refrigerant tank is formed from a sealed tank having a pair of faced walls; a heating body (CPU) is fixed on one wall (heat-receiving wall) of the sealed tank; a radiation fin is fixed on another wall (radiation wall); and a predetermined quantity of refrigerant is stored in the sealed tank. Heat emitted by the heating body is transferred through the heat-receiving wall to the refrigerant in the sealed tank, boils the refrigerant, and is released as a latent heat of condensation as the vapor refrigerant condenses on the radiation wall. The latent heat of condensation is emitted from the radiation wall through the radiation fin into the atmosphere.
Furthermore, the cooling apparatus is formed in a manner that a liquid level of the refrigerant is maintained above a heating body mounting portion at which the CPU is mounted so that the refrigerant is boiled at the heating body mounting portion, even when a side-heat situation that the CPU is mounted on a side wall of the sealed tank (i.e., a pair of wall described above is arranged vertically).
However, in the case of the side-heat situation, the whole area of the heating body mounting portion may not be soaked in the refrigerant, a boiling area may decrease, and then a superheat degree of the heating body mounting portion may increase. On the other hand, at the radiation wall side, much area of the radiation wall is soaked in the refrigerant, a condensing area may decrease, and then a supercool degree of the heat-receiving wall may increase.